1. Field of the Invention
This invention relates generally to transmission of signals, and, more particularly, to verifying and correcting error in transmission path of signals.
2. Description of the Related Art
The telecommunications sector is undergoing a major metamorphosis. The change has been induced by three primary factors. First is the growing number of users demanding more bandwidth for faster data transmission. Second is the congestion in the Plain Old Telephone Service (POTS), designed for transmission of voice signals in analog form. Third is the Telecommunications Reform Act, which is fostering broader competition through deregulation. All three of the aforementioned factors call for a more effective and efficient means for transporting data at high speeds.
To meet the demand for high-speed communication, designers are seeking innovative and cost-effective solutions that take advantage of the existing network infrastructure. Several technological advancements have been made in the telecommunications industry that make use of the existing network of telephone wires. The most promising of these technologies is the Digital Subscriber Line (DSL) technology.
DSL is making the existing network of telephone lines more robust and versatile. Once considered virtually unusable for broadband communications, an ordinary twisted pair equipped with DSL interfaces can transmit videos, television, and very high-speed data. The fact that more than six hundred million telephone lines exist around the world is a compelling reason that these lines will serve as the primary transmission conduits for at least several more decades. Because DSL utilizes telephone wiring already installed in virtually every home and business in the world, it has been embraced by many as one of the more promising and viable options.
There are now at least four popular versions of DSL technology, namely Asymmetrical Digital Subscriber Line (ADSL), Integrated Services Digital Network Digital Subscriber Line (IDSL), Very High-Speed Digital Subscriber Line (VDSL), and Symmetric Digital Subscriber Line (SDSL). Although each technology is generally directed at different types of users, they all share certain characteristics. For example, all four DSL systems utilize the existing, ubiquitous telephone wiring infrastructure, deliver greater bandwidth, and operate by employing special digital signal processing. The variations of DSL technologies are commonly referred to as xDSL technology. Because xDSL technology is well known in the art, they will not be described in detail herein.
DSL, as well as its later siblings, is making it possible for users to communicate over normal telephone wires at a much faster rate than before. The different flavors of DSL will converge around specific market niches and applications. For example, home users may favor ADSL for uses such as video-on-demand and Internet access. On the other hand, small businesses could find IDSL attractive for telecommuting and high-speed data transmission. Large businesses might choose VDSL to deliver Internet traffic or limited multimedia traffic to large businesses. DSL technologies leave Plain Old Telephone Service undisturbed. Traditional analog voice band interfaces use the same frequency band, 0-4 Kilohertz (KHz), as telephone service, thereby preventing concurrent voice and data use. A DSL interface, on the other hand, operates at frequencies above the voice channels, from around 30 KHz to 1.1 Megahertz (MHz). Thus, a single DSL line is capable of offering simultaneous channels for voice and data.
DSL systems use digital signal processing (DSP) to increase throughput and signal quality through common copper telephone wire. It provides a downstream data transfer rate Iraq from the DSL Point-of-Presence (POP) to the subscriber location at speeds of up to 8 Mega-bits per second (MBPS). The transfer rate of 1.5 MBPS, for instance, is fifty times faster than a conventional 28.8 kilobits per second (KBPS).
Although DSL and POTS systems can co-exist on one line (e.g., also referred to as xe2x80x9csubscriber linexe2x80x9d), the xDSL traffic is not passed through the POTS circuitry due to the different bandwidth, voltage, and power needs between the two systems. The xDSL signal is typically driven onto the subscriber line by a separate driver than is the POTS signal because the two signals are very different. The xDSL signal has a lower voltage, wider bandwidth, and often requires a different number of bits of resolution when digitized.
FIG. 1 illustrates a stylized block diagram of a communications system 100 that supports both xDSL and POTS technology. The communications system 100 depicts a typical xDSL and POTS installation between a Customer Premise (CP) 110 and Central Office (CO) 105. A subscriber line 120 links the CO 105 to the CP 110. The transmission of data signals over the subscriber line 120 from the CO 105 to CP 110 is typically referred to as a xe2x80x9cdownstreamxe2x80x9d transmission and the transmission of data signals from the CP 110 to CO 105 as an xe2x80x9cupstreamxe2x80x9d transmission.
As can be seen in FIG. 1, both the CP 110 and CO 105 utilize splitters 125, 130 to separate the different frequency bands that are transmitted over the subscriber line 120. In the illustrated communications system 100, the splitters 125, 130 separate the voice band frequencies from the data band frequencies. Accordingly, splitters 125, 130 comprise a voice filter 135, 140, which is typically a low-pass filter, and a data filter 145, 150, which is typically a high-pass filter. At the CO 105, the voice filter 135 substantially removes the data band frequencies from the signal on the subscriber line 120 before providing a signal on a line 155 to a CODEC 160. The data filter 145 at the CO 105, conversely, substantially removes the voice band frequencies and provides a signal on a line 165 to an xDSL processor 170. At the CP 110, the voice filter 140 substantially removes the data band frequencies from the signal on the subscriber line 120 before providing a signal on a line 175 to either a telephone 180 or a modem 182. The data filter 150 at the CP 110, conversely, substantially removes the voice band frequencies and provides a signal on a line 185 to an XDSL processor 190.
The communications system 100 of FIG. 1 suffers from several shortcomings in that it does not allow for an easy means to verify the connectivity between the CO 105 and CP 110, particularly with respect to the connectivity between the two xDSL processors 170, 190. Furthermore, the communications system 100 does not offer a quick and cost-efficient means for self-correcting the error, in case a connectivity error is detected. For example, one common connectivity error encountered is the incorrect installation of the splitters 125, 130, particularly the ones that are located at the CP 110. Splitters 125, 130 that are incorrectly installed (i.e. the connections to the data filter 145, 150 and the voice filter 135, 140 are reversed) prevent the voice/modem 180/182 and xDSL processor 170, 190 from receiving the voice and data band frequencies, respectively.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.
In one aspect of the present invention, a method is provided. The method includes providing an enable signal to a configuration device for generating a preselected signal, providing the preselected signal to a peer station over a subscriber line, and adjusting a transmission path of a signal to the peer station through the subscriber line in response to the preselected signal.
In one aspect of the present invention, an apparatus having a first and second terminal is provided. The apparatus includes a first switching device, a second switching device, and a configuration device. The first switching device includes an enable input terminal and an output terminal connected to the first terminal of the apparatus. The first switching device is capable of connecting the second terminal of the apparatus in response to an enable signal. The second switching device includes an enable input terminal and an output terminal coupled to the second terminal of the apparatus, wherein the second switching device is capable of connecting to the first terminal of the apparatus in response to an enable signal. The configuration device includes an enable input terminal, wherein the configuration device is capable of transmitting a preselected signal over a subscriber line to a peer station. The configuration device is also capable of providing the enable signal to the enable input terminal of the first switching device and to the enable input terminal of the second switching device.